This invention relates to an apparatus for opening and cleaning fiber material, particularly cotton and is of the type which has at least two rollers provided with a clothing (hereafter "clothed rollers") arranged downstream of a fiber feeding device, as viewed in a direction of fiber feed. At least two of the clothed rollers are provided with a mote knife associated with a waste removal clearance. The centrifugal forces at the circumference of the second clothed roller are greater than at the circumference of the first clothed roller arranged upstream of the second clothed roller as viewed in the direction of the advance of the fiber material.
In a known apparatus of the above-outlined type, as disclosed, for example, in German Offenlegungsschrift (non-examined published application) No. 2,712,650, first and second clothed rollers are serially arranged and are rotated in opposite directions. The second clothed roller has a smaller diameter and rotates with a significantly higher rpm than the first clothed roller and the points of the two clothings are in a fiber-transferring (doffing) position relative to one another. The vacuum present in a downstream-arranged screen drum extends back to the second clothed roller via a fiber conveying channel. After passing the waste removal clearance, the fiber material leaves the second clothed roller and is admitted to the screen drum. This occurrence is influenced by an intake air stream which passes through an opening in the housing and the waste removal clearance. According to another embodiment disclosed in the above-identified German Offenlegungsschrift, the first and second clothed rollers are associated with a third clothed roller which has the same diameter as the first clothed roller and which rotates codirectionally therewith but has a lower rpm. The clothing points of the first and the third clothed rollers are in a carding relationship with one another. The third clothed roller is surrounded by a housing interrupted by a waste removal clearance provided with a mote knife. In both embodiments the second clothed roller cooperates directly with the first clothed roller.
It has been found that in a prior art arrangement as described above, the suction air stream which takes off the fiber material from the second clothed roller has, disadvantageously, a feedback effect on the first clothed roller. It is particularly disadvantageous that the suction stream gains access to the region about the first clothed roller by extending through the intermediate space between the first clothed roller and the housing and thus adversely affects the guidance of the fiber. It is furthermore disadvantageous that by virtue of the intake air stream which is admitted from the outside, the suction air stream, together with the useful fiber tufts removed from the second clothed roller, also entrains trash from the waste removal clearance associated with the second clothed roller. The suction stream provided to advance the fiber material to the screen drum has a disadvantageous effect on the waste removal clearances associated with the first and second clothed rollers. It is yet another disadvantage of the above-described prior art construction that the fiber material, upon direct transfer from the first to the second clothed roller can be opened only as a result of particularly high rpm's which requires a structurally complex arrangement, and further, the rpm is limited by the critical bending rpm and the width of the clothed roller. Since the fiber material is insufficiently opened because of the significantly lower rpm's, the cleaning effect of the second clothed roller is altogether insufficient.